This disclosure relates to detection of animal distress, and particularly to notification of caregivers of such distress. Excluding old age, colic is the leading cause of death in domesticated horses regardless of breed, sex, and usage. It is estimated that this condition afflicts nearly 5% of horses in the US each year and more than 11% of these cases will be fatal. Being cast, although seldom traumatic, is another highly-common cause of serious injury to horses. Unfortunately, colic and being cast often occur overnight or at remote locations when horses are unsupervised, resulting in delayed intervention. Delayed intervention is a negative prognostic indicator that has dire impact on survival and quality-of-life outcomes. Another important time for equine surveillance is when a pregnant mare (i.e., adult female horse) is scheduled to foal (i.e., give birth). This process occurs very quickly and while the majority of mares foal without difficulties, a meaningful percentage experience complications that require human intervention to reduce the risk of injury or death of the foal or mare.
Colic
Colic is one of the most dangerous and costly equine medical problems. Colic is a symptom of disease, but not a disease itself, and is generally defined as any abdominal pain. Equine colic can involve any number of abdominal organs, not just the gastrointestinal tract. For example, abdominal discomfort from kidney or liver disease will sometimes cause signs of colic. Equine colic can originate from the stomach, small intestine, large intestine, or some combination thereof, and is associated with any malfunction, displacement, twisting, swelling, infection, or lesion of any part of the equine digestive system.
Equine colic is multifaceted and its diagnosis can be elusive with symptoms ranging from subjective and subtle changes in the animal's attitude (e.g., depression) to objective changes in the animal's vital signs (e.g., increased heart and respiratory rates, heart rate variability, rise in temperature), biologic functions (e.g., lack of digestion), and actions/movements (e.g., pawing, kicking, flank watching, rising/falling, rolling+/−thrashing). Further, a horse in distress will not usually display a healthy shake upon rising/standing after rolling or lying down. A horse suffering from colic may show any number of the following signs:                Pawing and/or scraping (front legs)        Kicking (back legs) up, or at abdomen        Repeated lying down and rising/standing        Rolling (+/−thrashing)        Stretching        Pacing        Flank watching (i.e., turning of the head to watch stomach and/or hind quarters)        Biting/nipping the stomach        Repeated flehmen response (i.e., curling of upper lip)        Groaning        Bruxism (i.e., excessive grinding of the teeth or clenching of the jaw)        Excess salivation        Loss of appetite        Change in attitude; depression        Frequent attempts to urinate        Lack of normal digestive/gut noise        Lack of defecation        Increased heart rate        Increased respiratory rate        Increased temperature        Sweating        
The causes of colic are not absolute and may include, but are not limited to:                Obstruction of the gastrointestinal tract from food or other materials        Impaction of food material in the gastrointestinal tract        Buildup of gas inside of the abdomen        Parasitic infestation by roundworms, tapeworms, cyathostomes, and/or strongyles        Dorsal displacement        Torsion of the gastrointestinal tract        Intussusceptions        Epiploic foramen entrapment        Strangulating lipoma        Mesenteric rent entrapment        Gastric ulceration        Enteritis        Colitis        
While many animals can suffer from colic, horses—especially those that are stabled—are particularly susceptible due to a multitude of factors, including heavy grain-based diets, relatively small stomach volume, the inability to release excess gas by eructation, susceptibility to parasitic infestation, and a highly convoluted gastrointestinal tract. Treatment for equine colic varies depending on the cause and severity of the condition ranging from rest and medication to invasive emergency surgery. Different types of colic include, but are not limited to:                Stomach distention: The small capacity of a horse's stomach makes it susceptible to distension when excessive amounts of food are ingested. When a horse gorges itself on grain, or a substance which expands when dampened like dried beet pulp, the contents of the stomach can swell. Unlike humans, horses have a valve at the distal end of their esophagus into the stomach that only opens only one way, and as a result horses cannot regurgitate. If something is eaten to disrupt their digestives system, there is only one direction digesta can travel. The horse's small stomach and their inability to regurgitate may result in distension and potential rupture of the stomach.        Displacement: The small intestine is suspended in the abdominal cavity by the mesentery and is free floating in the gut. In a displacement, a portion of the intestine has moved to an abnormal position in the abdomen. This mobility can predispose the small intestine to become twisted. Except in rare cases, the result is total blockage of the intestine requiring immediate surgery. During twisted intestine surgery, the intestine is repositioned and any portion of the intestine that is damaged due to restricted blood flow is removed. Displacement colic can be caused by gas build up in the gut that makes the intestines buoyant and subject to movement within the abdominal cavity.        Impaction colic: Impaction colic occurs when the intestine becomes blocked by a food mass that's too large to easily pass. The large intestine folds upon itself and has several changes of direction (flexures) and diameter changes. These flexures and diameter shifts can be sites for impactions, where a firm mass of feed or other foreign material blocks the intestine. Impactions can be induced by coarse feed stuff, dehydration, or accumulation of foreign material.        Gas colic: Most cases of colic are associated with some gas build up. Gas can accumulate in the stomach as well as the intestines. As gas builds up, the gut distends, causing abdominal pain. Excessive gas can be produced by bacteria in the gut after ingestion of large amounts of grain or moldy feeds. The symptoms of gas colic are usually highly painful but non-life threatening unless untreated, and then displacement becomes a possibility.        Spasmodic colic: This occurs due to increased contractions of the smooth muscle in the intestines. These intestinal contractions, or abnormal spasms, cause the intestines to contract painfully. Over-excitement or over-stress of the animal can trigger spasmodic colic.        Sand colic: When fed on the ground in sandy regions sand can accumulate in the horse's cecum. The irritation can cause discomfort, and if there are significant amounts of sand present, the weight can cause the cecum to become displaced.        Enteritis/colitis: In some cases, abdominal pain is due to inflammation of the small intestine (enteritis) or large intestine (colitis). These conditions are the result of inflammation of the intestine, and may be caused by bacteria, grain overload, or tainted feed. Horses with enteritis/colitis may also have diarrhea. Enteritis and colitis are often hard to diagnose and may present themselves similar to displacement or impaction colic.        Parasite infections: Certain types of parasitic infections can cause colic. Strongyles, a type of parasitic worm, cause intestinal damage that can restrict blood flow to the intestine. Damage to the walls of the intestine produce a roughened surface that can accumulate clots. Other colic producing parasites in horses include ascarids (roundworms) and bot flies which can cause stomach blockage resulting in colic.        Stress: Travel, herd changes, schedule disruptions, and other traumatic events can contribute to stress in an animal which may result in colic.Being Cast        
Being cast occurs when a horse lies down or rolls in a stall and gets trapped too closely to the wall. When this occurs, the horse is not able to gain sufficient leverage and stand up. Subsequently, the horse may become frightened and begin thrashing, likely resulting in injury. Exhaustion to the point of shock is another concern with a distressed horse that is cast.
Nearly all cases of being cast require human intervention to assist the animal to turn over. If the horse is relatively quiet, two persons may be able to reposition the horse by pulling it over gently by the tail or hind legs (with the aid of a lunge line), while simultaneously pulling the horse's head over. If the horse is panicked, sedation may be required before any attempt is made to reposition and turn over the horse.
Foaling
Birthing a foal normally takes place over several hours and in three stages so it's critical for a caretaker to recognize these stages and assess whether intervention is needed. However, monitoring of pregnant mares by caretakers is often impractical and challenging, especially during the last few weeks of the normal 340-day gestation period where round-the-clock (24/7) surveillance is warranted.
In normal undisturbed equine pregnancies, a normal fetal heart rate (HR) is 110-115 beats per minute (BPM) during days 170-240 of gestation. However, this decreases to 80-85 BPM 3 weeks prior to birth and 78-80 BPM 1 day prior and before parity with the mare's increased HR at the time of birth. Interestingly, as fetal HR decrease through gestation, fetal respiratory rate (RR) can more than double from 10-12 to 26-28 breaths per minute at the time of birth. As such, having the ability to simultaneously monitor both fetal and maternal HRs in horses may serve as a useful approach to predicting the onset of parturition.
Fetomaternal electrocardiography (ECG) is reliable method for assessing fetal cardiac activity over time, including fetal HR. However, continuous real-time monitoring in the field is challenging and often difficult because of the mare's natural intestinal sounds and large size, so two other methods are commonly used. The first is ultrasonography, which can be done transrectally during early gestation and transabdominally as gestation advances and as the fetus descends into the mare's abdomen. Second is transcutaneous Doppler monitoring for fetuses in later gestation. Not unlike fetomaternal ECGs, real-world application of these methodologies is suboptimal as the signal is often intermittent, and both are labor-intensive, invasive, and expensive.
Stage 1: Positioning of the Foal                During this stage (1-4 hours) the fetus gradually shifts from a position on its back and rotates until its heads and forelimbs are extended in the birth canal. Over several hours the pregnant mare may appear restless and become very nervous. She will likely have several transient periods of pacing, walking the fence line, and colic-like symptoms (e.g., pawing, kicking, rising/falling+/−healthy shake, rolling+/−thrashing). Mares in the pasture will also move away from other horses and towards complete isolation.        
Stage 2: Delivery of the Foal                During this stage (15-20 minutes) the fetus moves down the birth canal, the mare's water breaks, and the foal is born. Due to very strong contractions of the abdominal and uterine wall muscles, the mare usually lies on her side (i.e., on her flanks) with her legs fully extended although she may also rise/fall several times to reposition the foal, sometimes with the foal's head and limbs protruding. During this stage it's important for the caretaker to check the position of the foal within the vagina; lower the foal to the ground if the mare is standing; reposition the mare away from any wall, fence, or other obstacle; and break open the amniotic sack and untangle the umbilical cord, if required.        
Stage 3: Expulsion of the Placenta                During this final stage (1-8 hours), the placenta is expulsed. If the placenta has not been expulsed after 3 hours, the caretaker should alert a veterinarian. It is also important for the caretaker to tie-up the afterbirth in a knot such that it hangs over the mare's hocks during this period.Problems with Current Technology        
Although there are a few technologies (i.e., equine foaling/birthing monitors) on the market today, all these products have serious shortcomings. Their cumbersome design, rudimentary analytical methods, and limitations in wireless transmissions prevent them from being used reliability on a large scale as foaling/birthing monitors, let alone secondary use to assist in detecting colic, being cast, or other distress states of animals.
Belly Bands: In practice, horses tend to become preoccupied with nipping at belly bands, making it a distraction for horses and staff. The belly band also introduces a new injury risk due to the transmitter unit mounted on the horse's back. A horse experiencing severe colic is likely to roll frequently and often. As such, a horse wearing the unit on its back is likely to roll onto the unit, which may result in a back injury. The methods for mounting this, which are similar to other foaling sensors on the market today, and the positioning of these sensors on a horse make them suboptimal for the detection of colic.
Behavior Analysis: Most foaling/birthing monitors rely solely on motion sensors to assess whether an animal is lying down or on its side for a specific period of time, which is likely to be plagued with many false-positive findings.
Radio Frequency Transmission: A few systems use simple radio frequency (RF) transmitters to signal an alarm when triggered. These systems can be connected to a phone line or pager to automatically alert caretakers. These systems use single-channel RF modulation to transmit sensor data. Because multiple transmitters interfere with each other and their surroundings (e.g., metal barns), the RF approach cannot be scaled-up for large operations with many horses or be used while in transit. Interference can also arise from other RF transmitters, such as cordless phones or other similar devices located nearby.
Animal health monitoring system present challenges in terms of outdoor environments, impact and removal by the animal due to discomfort or bulkiness of system enclosure, and the like. Accordingly, improvements are sought in the wearability and survivability of such systems.
Given the deficiencies of the technologies cited above, barn managers resort to (if anything) round-the-clock night checks by caretakers and/or night watchmen to monitor the health and safety of their horses. Such laborious checks by humans are time consuming, subjective, costly, and not without error. Even with individuals on location twenty-four hours a day in a veterinary facility or barn, signs of distress or trouble might not be caught as early as desired. Accordingly, improvements are sought in the detection of animal distress and notification of caregivers. The present invention remedies many of these problems and limitations.